Fluid transport systems are well known and used in a number of applications. For example, heated fluids, such as melted chocolate, candy, or waxes, may be transported from one station to another during a manufacturing process. Other fluids, such as milk or beer, may be cooled and transported through conduits in a facility. Viscous materials, such as soap, lubricants, or food sauces, may require thermal treatment before being moved through a machine or facility.
One specific application of transporting a thermally treated fluid in a machine is the transportation of ink that has been melted from a solid ink stick in a phase change printer. Solid ink or phase change ink printers conventionally use ink in a solid form, either as pellets or as ink sticks of colored cyan, yellow, magenta and black ink, that are inserted into feed channels through openings to the channels. Each of the openings may be constructed to accept sticks of only one particular configuration. Constructing the feed channel openings in this manner helps reduce the risk of an ink stick having a particular characteristic being inserted into the wrong channel. U.S. Pat. No. 5,734,402 for a Solid Ink Feed System, issued Mar. 31, 1998 to Rousseau et al.; and U.S. Pat. No. 5,861,903 for an Ink Feed System, issued Jan. 19, 1999 to Crawford et al. describe exemplary systems for delivering solid ink sticks into a phase change ink printer.
After the ink sticks are fed into their corresponding feed channels, they are urged by gravity or a mechanical actuator to a heater assembly of the printer. The heater assembly includes a heater that converts electrical energy into heat and a melt plate. The melt plate is typically formed from aluminum or other lightweight material in the shape of a plate or an open sided funnel. The heater is proximate to the melt plate to heat the melt plate to a temperature that melts an ink stick coming into contact with the melt plate. The melt plate may be tilted with respect to the solid ink channel so that as the solid ink impinging on the melt plate changes phase, it is directed to drip into the reservoir for that color. The ink stored in the reservoir continues to be heated while awaiting subsequent use.
Each reservoir of colored, liquid ink may be coupled to a print head through at least one manifold pathway. As used herein, liquid ink refers to solid ink that has been heated so it changes to a molten state or liquid ink that may benefit from being elevated above ambient temperature. The liquid ink is pulled from the reservoir as the print head demands ink for jetting onto a receiving medium or image drum. The print head elements, which are typically piezoelectric devices, receive the liquid ink and expel the ink onto an imaging surface as a controller selectively activates the elements with a driving voltage. Specifically, the liquid ink flows from the reservoirs through manifolds to be ejected from microscopic orifices by piezoelectric elements in the print head.
Printers having multiple print heads are known. The print heads in these printers may be arranged so a print head need not traverse the entire width of a page during a printing operation. The print heads may also be arranged so multiple rows may be printed in a single operation. Each print head, however, needs to receive each color of ink in order to print the image portion allotted to the print head. One method of accomplishing this task requires each print head to have a separate feed channel and reservoir for each color. The typically large structure to accommodate this method, however, consumes too much space in the printer.
One approach is to couple each reservoir containing an ink color to all of the print heads in the printer. In a typical printer that uses four colors for printing, four reservoirs are provided with each reservoir collecting melted ink for one of the four colors. Thus, 4n connections are required to supply each print head with all of the printing colors, where n is the number of print heads. The resulting number of connections for printers having multiple print heads presents issues. One issue is the length of the connections to the various print heads. The distance from a more remote print head to a reservoir may be sufficient to allow the ambient air temperature to remove enough heat from the melted ink that the ink solidifies. To address this issue, each connection may be independently heated as disclosed in commonly assigned, co-pending U.S. patent application entitled “System For Maintaining Temperature Of A Fluid In A Conduit,” which was filed on Dec. 20, 2006 and identified by Ser. No. 11/642,801, and which issued as U.S. Pat. No. 7,753,512 on Jul. 13, 2010. Independently heating a significant number of connections, however, may adversely impact the energy efficiency of the printer. Therefore, a more cost effective structure for maintaining the temperature of melted ink in a plurality of connections between a plurality of print heads and a plurality of ink reservoirs would be useful.